WordPress Admin Menu Hierarchy Correction

wp-admin-menu-hierarchy-correction.php

<?php
function wpmark_menu_hierarchy_correction( $parent_file ) {
	
	global $current_screen;
	
	/* get the base of the current screen */
	$screenbase = $current_screen->base;

	/* if this is the edit.php base */
	if( $screenbase == 'edit' ) {

		/* set the parent file slug to the custom content page */
		$parent_file = 'wpmark_admin_menu';
		
	}
	
	/* return the new parent file */	
	return $parent_file;
	
}
add_action( 'parent_file', 'wpmark_menu_hierarchy_correction', 999 );